diff --git a/src/builder/code.rs b/src/builder/code.rs
new file mode 100644
index 0000000..a2dd102
--- /dev/null
+++ b/src/builder/code.rs
@@ -0,0 +1,141 @@
+use super::invoke::{Invoke, Identity};
+use elements;
+
+pub enum Signature {
+    TypeReference(u32),
+    Inline(elements::FunctionType),
+}
+
+pub struct SignatureBuilder<F=Identity> {
+    callback: F,
+    signature: Signature,
+}
+
+impl<F> SignatureBuilder<F> where F: Invoke<Signature> {
+    pub fn with_callback(callback: F) -> Self {
+        SignatureBuilder { 
+            callback: callback, 
+            signature: Signature::TypeReference(0) 
+        }
+    }
+
+    pub fn type_ref(mut self, val: u32) -> Self {
+        self.signature = Signature::TypeReference(val);
+        self
+    }
+
+    pub fn param(mut self, value_type: elements::ValueType) -> Self {
+        {
+            let signature = &mut self.signature;
+            if let Signature::TypeReference(_) = *signature { 
+                *signature = Signature::Inline(elements::FunctionType::default())
+            }
+
+            if let Signature::Inline(ref mut func_type) = *signature {
+                func_type.params_mut().push(value_type);
+            }
+        }
+
+        self
+    }
+
+    pub fn return_type(mut self, value_type: elements::ValueType) -> Self {
+        {
+            let signature = &mut self.signature;
+            if let Signature::TypeReference(_) = *signature { 
+                *signature = Signature::Inline(elements::FunctionType::default())
+            }
+
+            if let Signature::Inline(ref mut func_type) = *signature {
+                *func_type.return_type_mut() = Some(value_type);
+            }
+        }
+                
+        self
+    }
+
+    pub fn build(self) -> F::Result {
+        self.callback.invoke(self.signature)
+    }
+}
+
+pub struct FunctionsBuilder<F=Identity> {
+    callback: F,
+    section: Vec<Signature>,
+}
+
+impl FunctionsBuilder {
+    /// New empty functions section builder
+    pub fn new() -> Self {
+        FunctionsBuilder::with_callback(Identity)
+    }
+}
+
+impl<F> FunctionsBuilder<F> {
+    pub fn with_callback(callback: F) -> Self {
+        FunctionsBuilder {
+            callback: callback,
+            section: Vec::new(),
+        }
+    }
+
+    pub fn with_signature(mut self, signature: Signature) -> Self {
+        self.section.push(signature);
+        self
+    }
+
+    pub fn signature(self) -> SignatureBuilder<Self> {
+        SignatureBuilder::with_callback(self)
+    }
+}
+
+impl<F> Invoke<Signature> for FunctionsBuilder<F> {
+	type Result = Self;
+
+	fn invoke(self, signature: Signature) -> Self {
+		self.with_signature(signature)
+    }    
+}
+
+impl<F> FunctionsBuilder<F> where F: Invoke<elements::FunctionsSection> {
+    pub fn build(self) -> F::Result {
+        let mut result = elements::FunctionsSection::new();
+        for f in self.section.into_iter() {
+            if let Signature::TypeReference(type_ref) = f {
+                result.entries_mut().push(elements::Func::new(type_ref));
+            } else {
+                unreachable!(); // never possible with current generics impl-s
+            }
+        }
+        self.callback.invoke(result)
+    }
+}
+
+pub type SignatureBindings = Vec<Signature>;
+
+impl<F> FunctionsBuilder<F> where F: Invoke<SignatureBindings> {
+    pub fn bind(self) -> F::Result {
+        self.callback.invoke(self.section)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+
+    use super::FunctionsBuilder;
+
+    #[test]
+    fn example() {
+        let result = FunctionsBuilder::new()
+            .signature().type_ref(1).build()
+            .build();
+
+        assert_eq!(result.entries().len(), 1);
+
+        let result = FunctionsBuilder::new()
+            .signature().type_ref(1).build()
+            .bind();      
+
+        assert_eq!(result.len(), 1);              
+    }
+}
\ No newline at end of file
diff --git a/src/builder/invoke.rs b/src/builder/invoke.rs
new file mode 100644
index 0000000..6fe8bdb
--- /dev/null
+++ b/src/builder/invoke.rs
@@ -0,0 +1,15 @@
+//! invoke helper
+
+pub trait Invoke<A> {
+	type Result;
+
+	fn invoke(self, arg: A) -> Self::Result;
+}
+
+pub struct Identity;
+
+impl<A> Invoke<A> for Identity {
+	type Result = A;
+
+	fn invoke(self, arg: A) -> A { arg }
+}
\ No newline at end of file
diff --git a/src/builder/mod.rs b/src/builder/mod.rs
new file mode 100644
index 0000000..f41fd90
--- /dev/null
+++ b/src/builder/mod.rs
@@ -0,0 +1,7 @@
+//! Various builders to generate/alter wasm components
+
+mod invoke;
+mod module;
+mod code;
+
+pub use self::module::{module, ModuleBuilder};
\ No newline at end of file
diff --git a/src/builder/module.rs b/src/builder/module.rs
new file mode 100644
index 0000000..1cec56b
--- /dev/null
+++ b/src/builder/module.rs
@@ -0,0 +1,76 @@
+use super::invoke::{Invoke, Identity};
+use super::code::FunctionsBuilder;
+use elements;
+
+/// Module builder
+pub struct ModuleBuilder<F=Identity> {
+    callback: F,
+    sections: Vec<elements::Section>,
+}
+
+impl ModuleBuilder {
+    /// New empty module builder
+    pub fn new() -> Self {
+        ModuleBuilder::with_callback(Identity)
+    }
+}
+
+impl<F> ModuleBuilder<F> where F: Invoke<elements::Module> {
+    /// New module builder with bound callback
+    pub fn with_callback(callback: F) -> Self {
+        ModuleBuilder {
+            callback: callback,
+            sections: Vec::new(),
+        }
+    }
+
+    /// Fill module with sections from iterator
+    pub fn with_sections<I>(mut self, sections: I) -> Self 
+        where I: IntoIterator<Item=elements::Section>
+    {
+        self.sections.extend(sections);
+        self
+    }
+
+    pub fn with_section(mut self, section: elements::Section) -> Self {
+        self.sections.push(section);
+        self
+    }
+
+    pub fn functions(self) -> FunctionsBuilder<Self> {
+        FunctionsBuilder::with_callback(self)
+    }
+
+    /// Build module (final step)
+    pub fn build(self) -> F::Result {
+        self.callback.invoke(elements::Module::new(self.sections))
+    }
+}
+
+impl<F> Invoke<elements::FunctionsSection> for ModuleBuilder<F> 
+    where F: Invoke<elements::Module>
+{
+	type Result = Self;
+
+	fn invoke(self, section: elements::FunctionsSection) -> Self {
+		self.with_section(elements::Section::Function(section))
+    }    
+}
+
+/// Start new module builder
+pub fn module() -> ModuleBuilder {
+    ModuleBuilder::new()
+}
+
+#[cfg(test)]
+mod tests {
+
+    use super::module;
+
+    #[test]
+    fn smoky() {
+        let module = module().build();
+        assert_eq!(module.sections().len(), 0);
+    }
+
+}
diff --git a/src/elements/mod.rs b/src/elements/mod.rs
index b798c7b..77a3f8c 100644
--- a/src/elements/mod.rs
+++ b/src/elements/mod.rs
@@ -14,7 +14,10 @@ mod func;
 mod segment;
 
 pub use self::module::Module;
-pub use self::section::Section;
+pub use self::section::{
+    Section, FunctionsSection, CodeSection, MemorySection, DataSection,
+    ImportSection, ExportSection, GlobalSection,
+};
 pub use self::import_entry::{ImportEntry, MemoryType, TableType, GlobalType, External};
 pub use self::export_entry::{ExportEntry, Internal};
 pub use self::global_entry::GlobalEntry;
@@ -22,7 +25,7 @@ pub use self::primitives::{
     VarUint32, VarUint7, VarUint1, VarInt7, Uint32, 
     Uint64, VarUint64, CountedList, CountedWriter, CountedListWriter,
 };
-pub use self::types::{ValueType, BlockType};
+pub use self::types::{ValueType, BlockType, FunctionType};
 pub use self::ops::{Opcode, Opcodes, InitExpr};
 pub use self::func::{Func, FuncBody, Local};
 pub use self::segment::{ElementSegment, DataSegment};
diff --git a/src/elements/module.rs b/src/elements/module.rs
index 29a7d50..ecbcd28 100644
--- a/src/elements/module.rs
+++ b/src/elements/module.rs
@@ -10,6 +10,15 @@ pub struct Module {
 }
 
 impl Module {
+    /// New module with sections
+    pub fn new(sections: Vec<Section>) -> Self {
+        Module {
+            magic: 0x6d736100,
+            version: 1,
+            sections: sections,
+        }
+    }
+
     /// Version of module.
     pub fn version(&self) -> u32 { self.version }
 
diff --git a/src/elements/section.rs b/src/elements/section.rs
index 693a6b0..54a06c0 100644
--- a/src/elements/section.rs
+++ b/src/elements/section.rs
@@ -251,6 +251,14 @@ impl Serialize for ImportSection {
 pub struct FunctionsSection(Vec<Func>);
 
 impl FunctionsSection {
+    pub fn new() -> FunctionsSection {
+        FunctionsSection(Vec::new())
+    }
+
+    pub fn entries_mut(&mut self) -> &mut Vec<Func> { 
+        &mut self.0
+    }
+
     pub fn entries(&self) -> &[Func] {
         &self.0
     }
diff --git a/src/elements/types.rs b/src/elements/types.rs
index 9709407..ac40061 100644
--- a/src/elements/types.rs
+++ b/src/elements/types.rs
@@ -121,13 +121,27 @@ pub struct FunctionType {
     return_type: Option<ValueType>,
 }
 
+impl Default for FunctionType {
+    fn default() -> Self {
+        FunctionType {
+            form: 0x60,
+            params: Vec::new(),
+            return_type: None,
+        }
+    }
+}
+
 impl FunctionType {
     /// Function form (currently only valid value is `0x60`)
     pub fn form(&self) -> u8 { self.form }
     /// Parameters in the function signature.
     pub fn params(&self) -> &[ValueType] { &self.params }
+    /// Mutable parameters in the function signature.
+    pub fn params_mut(&mut self) -> &mut Vec<ValueType> { &mut self.params }
     /// Return type in the function signature, if any.
     pub fn return_type(&self) -> Option<ValueType> { self.return_type }
+    /// Mutable type in the function signature, if any.
+    pub fn return_type_mut(&mut self) -> &mut Option<ValueType> { &mut self.return_type }
 }
 
 impl Deserialize for FunctionType {
diff --git a/src/lib.rs b/src/lib.rs
index 0263ff2..690bdcb 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -5,6 +5,7 @@
 extern crate byteorder;
 
 pub mod elements;
+pub mod builder;
 
 pub use elements::{
     Error as SerializationError,